Lubricants comprising polyphenyl ethers and mixed metal salts of fatty acids



United States Patent 3,198,734 LUBRICANTS COMPRISHNG POLYPIENYL ETHERSAND MIXED METAL SALTS 0F FATTY ACIDS Arnold J. Morway, Clark, N.J.,assignor to Esso Research and Engineering Company, a corporation ofDelaware No Drawing. Filed June 28, 1961, Ser. No. 120,150 3 Claims.(Cl. 252-17) 3,198,734 Patented Aug. 3, 1965 "ice This invention relatesto lubricating compositions comprising mixed metal salts of fatty acidsin a polyphenyl ether base oil, and methods for preparation of saidlubricating compositions. Particularly, the invention relates tolubricating greases and fiuids, which are suitable for high temperatureuse, comprising polyphenyl ether and alkaline earth metal salts of a Cto (3., fatty acid and a C to C fatty acid.

Recently, lubricating compositions containing mixed alkaline earth metalsalt of low molecular weight fatty acid and alkaline earth metal salt ofhigher molecular Weight fatty acid, have found Wide spread use incommercial applications. These lubricants are generally prepared byconeutralizing with lime, four or more mol equivalents of acetic acid(or its anhydride) per mole of higher fatty acid (such as oleic acid orcoconut acids). The resulting mixed salt lubricants have good anti-wearand load-carrying ability, and have gained widespread commercialacceptance. The commercial mixed-salt lubricants have generally beenprepared using a mineral oil base. However, during high temperature usefor extended periods, e.g. at temperatures of 400 F. and above, such asare encountered in lubrication of aircraft, rocket engines, steel makingfacilities, etc., the mineral oil compositions do not give good resultsbecause of the volatility of mineral oil. A wide variety of base oilshave been tested in order to form suitable mixed-salt lubricants forhigh temperature use. Thus, highly refined mineral oils and syntheticoils such as diesters of dicarboxylic acids, polyoxyalkylene glycols(Ucon oils), silicone oils, etc. have been tested. Even though a numberof these oils have been recognized as having good stability at hightemperatures, they did not possess the desired characteristics for hightemperature bearing lubrication when used as base oils for the mixedsalts referred to above. Recently, certain aryl-alkyl silanes such asdilauryl, diphenyl silane were found to form good mixed salt lubricantsfor high temperature use. It has now been found that a certain range ofpolyphenyl ethers are superior in several respects to the aforementionedsilane oil, which heretofore had been the best oil known to the presentinventors for high temperature mixed salt lubricants.

The polyphenyl ether oils of the invention are those normally liquid (at77 F.) ethers represented by the general formula:

Where n is about 3 to 6. The oxygen atoms attached to the hydrocarbonrings intermediate the terminal phenyl groups, can be in an ortho, meta,or para position relative etc.

The lubricating compositions of the invention will comprise a majoramount of polyphenyl ether as the base oil and about 5 to 40 wt.percent, preferably 10 to 30 wt. percent, of the mixed salt. .The mixedsalt in turn, will comprise a mixture of the alkaline earth metal saltsof a low molecular weight C to C fatty acid (preferably acetic acid oracetic anhydride) and a C to C fatty acid. Usually about 4 to 30,preferably 4 to 15, mol equivalents of low molecular weight acid per molequivalent to C to C fatty acid will be used.

The mixed salt thickener can be prepared by reacting alkaline earthmetal base, such as the hydroxides are carbonates of calcium, barium,strontium or magnesium, with the mixture of fatty acids. Calcium is thepreferred metal, being generally used in the form of a lime slurry,while acetic acid, or its anhydride, is preferably used as the lowmolecular weight acid.

The C to C fatty acids can be considered as including two groups, theintermediate molecular weight fatty acids and the high molecular Weightfatty acids. The intermediate molecular weight fatty acids are generallyconsidered to be the C to C acids, including straight chain, saturatedacids such as capric, caprylic, pelargonic acid, lauric acid, etc. Thehigh molecular weight fatty acids are generally considered to be the Cto C acids, such as stearic, 12-hydroxy stearic, oleic, tallow acids,hydrogenated fish oil acids, iso oleic, etc. The fatty acids can also beused in the form of their glycerides.

A high molecular weight fatty acid used in several examples of theinvention was a commercial iso-oleic acid. Iso-oleic can be regarded asthe cis form of oleic acid. The cis form is also known as elaidic acid.Commercial iso-oleic acid generally constitutesmixtures of a majoramount of elaidic acid with minor amounts of oleic acid (i.e.9-0ctadeceneoic acid) and other related acids such as l2-octadeceneoic,lin-oleic, linolic, stearic, palmitic, etc. The commercial iso-oleicacid used in the working examples of the invention is available underthe tradename of Emery 635 Fatty Acid.

If desired, various inorganic acids can be used to replace part of thelow molecular weight fatty acid component in the preparation of themixed salt material. Thus, strong mineral acids such as hydrochloricacid, nitric acid, sulfuric acid and orthophosphoric acid can be used.If phosphoric acid is used to replace a portion of the low molecularweight fatty acid, the resulting grease is made more resistant to colorand oxidation degradation than if no phosphoric acid was used. Variousinorganic salts such as alkaline earth metal or alkali metal (e.g.sodium and lithium) nitrites, phosphates, chromates, and carbonates canalso be added to the lubricant. If the metal component of the inorganicsalt is an alkaline earth 3 metal, then the salt can generally be formedfrom the appropriate acid, in situ, during the neutralization of thefatty acids.

The base oil is preferably 100 polyphenyl ether, but minor amounts ofother base oils can be added.

The compositions of the invention can be prepared in several ways. Inone method, all the acids are dispersed in the base oil and neutralizedwith the metal base. The water of reaction may be left in the lubricantby not applying heat, thereby forming a cold-sett lubricant. However,generally the product will be heated to about 225 to 600 F. to dehydratethe mixture. Preferably, the mixed salts are formed by co-neutralizingthe acids with metal base in the presence of a volatile inert solventsuch as Varsol No. 1 (a commercial hydrocarbon solvent marketed by theEnjay Co.), heptaue, toluene, etc. The resulting mixture is then mixedwith polyphenyl ether and the volatile solvent is evaporated by heating.

A more specific description of the preferred process is as follows: T heacids and metal base are added to the inert volatile solvent andintimately mixed. The heat of reaction will usually raise thetemperature of the reaction mass, but temperatures above about 200 F.are to be avoided at this phase of the process, so cooling may benecessary. The resulting composition will be relatively fluid due to thesolubil-izing efiect of the volatile solvent upon the resulting mixedfatty acid salts. The composition is then preferably homogenized andfiltered. This filtration step will eliminate unreacted metal base aswell as various contaminants of commercial metal base. For example, inthe case of lime, this filtration will remove calcium carbonate, iron,alumina oxide and silica. Some of these contaminants act as abrasives inclose clearance high shear applications, such as anti-friction bearings.After filtration, the volatile solvent concentrate of the mixed salts isadded to the polyphenyl ether oil. The resulting mass then is preferablyheated to temperatures of about 250 to 450 F., preferably 300 to 350 F,in order to dehydrate the mixture and to drive off the volatile solvent.The mixture can then be cooled to about 200 to 210 F., Whereconventional additives, if any, can be added. The lubricant is thenpreferably cooled to below 150 P. where it can be homogenized, as bypassing through a Gaulin homogenizer or a Charlotte mill, followed bysubsequent cooling to room temperature. If desired, grease concentratesof the mixed salts in the polyphenyl ether can be made by the abovetechniques and then diluted with additional lubricating oil to form thefinal grease composition, or even further diluted to form a fluid typelubricant.

The advantages of using the volatile solvent technique described aboveare: the ability to obtain a more complete reaction of the ingredientsdue to the lower viscosity of the reaction mass because of the lowviscosity solvent and its solubilizing effect, and .freedom frompossible side reactions with polyphenyl ether.

Conventional additives, which can be added to the compositions of theinvention, include oxidation inhibitors such as phenyl-a-naphthylamine;rust preventives such as sodium nitrite; other thickeners such aspolyethylene, polypropylene, carbon black, metal soaps; etc.

The invention will be further understood by reference to the followingexamples which include a preferred ernbodiment of the invention andwherein all parts are by weight.

EXAMPLE I Part A.13.4 parts of hydrated lime, and parts of iso-oleicacid (Emery 635 Fatty Acid) were mixed into 57.6 parts of Varsol No. lto form a smooth slurry. Next, 18 parts of glacial acetic acid wasslowly added as the heat .of reaction raised the temperature to about200 F. The composition was then cooled, homogenized by passing through aMorehouse mill having 0.003" clearance and then filtered through a 100mesh screen.

Part B.100 parts of the composition of Part A was then blended with 75parts of polyphenyl ether (Monsantos OS-124) by slowly pouring thepolyphenyl ether into the salt composition while stirring. Thetemperature of the resulting mixture was then slowly raised to about 350F., While mixing, thereby volatilizing approximately all of the water ofreaction and the Varsol. The residue was then cooled to 200 R, where 1part of phenyl-alphanaphthylamine was added. Following this thecomposition was further cooled to about P. where it was homogenized bypassage through a Morehouse mill having 0.003" clearance.

Mineral oil comparison grease A portion of the mixed salt-Varsolcomposition of Example I, Part A, was blended with a mineral lubricatingoil having a viscosity of 55 SUS at 210 F., by slowly pouring the oilinto the salt-Varsol composition, while stirring. The resulting mixturewas then heated to 350 F. to volatilize the water of reaction and theVarsol, then cooled to 200 P. where one part ofphenyl-alpha-naphthylamine was added. The composition was thenhomogenized in a Morehouse mill having 0.003" clearance at 90 F. Inother words, Example I, Part B, was repeated with the main exceptionthat mineral lubricating oil was used in place of the polyphenyl etheroil. Also, a slightly lesser amount of phenyl-alpha-naphthylamine wasused.

Silane oil comparison example As previously mentioned, the best hightemperature mixed salt lubricant previously known to the inventors wasone prepared from a dilauryl, diphenyl silane. This lubricant wasprepared as follows:

71.5 parts of Dow Corning QF-6-7009 Fluid (dilauryl, diphenyl silane),9.5 parts of hydrated lime and 2 parts of Hydrofol Acid Code 200 wereadded to an electrically heated grease kettle and intimately mixed. TheHydrofol Acid Code 200 is a commercial hydroxy stearic acid obtained byhydrogenating castor oil and consists of about 38 wt. percent 12-hydr0xystearic acid and 12 wt. percent of stearic acid. Next, a blendconsisting of 12 parts of glacial acetic acid and 4 parts of WecolineAAC acid was added to the kettle. Wecoline AAC acid is a commercial acidderived from coconut oil and consisting of about 26 wt. percent lauricacid, about 28 wt. percent caprylic acid and about 46 wt. percent capricacid. External heating was then initiated and the temperature of themixture was raised to about 430 F. and maintained at this temperaturefor about /2 hour. The heat was then shut off and the material wascooled to 200 F., at which point one part of phenyl-alpha-naphthylaminewas added as an oxidation inhibitor. Following this, the mixture wasallowed to cool to F. and was then pumped through a Morehouse millhaving a 0.003" clearance to form thefinished grease.

The properties and final compositions, in terms of ingredients, of thelubricants prepared above are summarized in the following Table I.

TABLE I Final Composition, Parts By Example Mineral Silane Weight I OilCom- Oil Comparison parison l5. 6 15. 6 12. 0 Iso-oleic Ac1d 8. 7 8. 7Wecoline AAC Ac 4. 0 Hydrofol Acid Code 200 2.0 Hydrated Lime 11. 6 11.6 9. 5 Phcnyla-naphthylamine 1. 2 1. 0 1. 0 Polyphenyl Ether 62. 9Mineral Lubricating Oil, 55 SUS.

at 210 F 63. 1 Diphenyl, Dilauryl silane 71. 5 Mole Ratio, Acetic/HigherFatty Acids 10/1 10/1 10/1 Properties: 7

Appearance Excellent Excellent Excellent Dropping Point, F None None None ASTM Penetration, 77 F., mm./10-

Unworlced 250 290 885 Worked 60 strokes. 255 300 225 Worked 10,000strokes 255 300 292 Solubility in Boiling Water". None None None F it Asseen by Table I, all three greases had no dropping points and the samemole ratios of acetic to the higher fatty acid. The advantage of thepolyphenyl ether oil grease (Example I) over the two comparison greasesis illustrated by the Lubrication Life test. This test is the standardspindle test of the Anti-Friction Bearing ManufacturersAssociation-National Lubricating Great Institute (AFBNA-NLGI). The testis carried out by determining the lubricating life of the grease inhours in a 204 mm. ball bearing rotating at 10,000 revolutions perminute.

The results obtained in the above test are summarized in Table II, whichfollows:

TABLE II.LUBRICATING LIFE IN 204 BALL BEARING As seen by Table II, asample of the grease of Example I ran for 2206 hours at 300 F. and wasstill in good condition. The test temperature was raised to 350 P. wherethe same sample performed satisfactory for an additional 522 hours or acumulative total of 2728 hours. At the end of this time, the grease wasstill soft and plastic. The test temperature of the bearing and greasewas then raised to 400 P. where the grease lubricated for another 372hours before failing. In comparison, the mineral oil comparison greasefailed after only 950 hours at 300 F. This grease had badly coked. Onesample of the silane oil comparison grease, ran for 1920 hours at 300 F.before failing, while a different sample ran for 1479 hours at 350 F.Although there was a slightly larger amount ofphenyl-alpha-naphthylamine in the grease of Example I as compared to thecomparison greases, previous experience indicates that this differencehad no substantial effect on the test results. Rather, the largedifference in test results are attributed to the base oils.

As a further example of the invention, Example I can be exactly repeatedbut using pure elaiclic acid rather than the commercial iso-oleic acid,and using in place of the commercial OS-124 phenyl ether, a polyphenylether of the structure:

What is claimed is: V

1. A method of preparing a lubricating composition which comprisesmixing C to 0., fatty acid and C to C fatty acid in a ratio of about 4to 30 mole equivalents of C to C fatty acid per mole equivalent of C toC fatty acid, with a neutralizing amount of alkaline earth metal base,in a volatile inert hydrocarbon solvent, adding polyphenyl ether of thegeneral formula:

where n is 3 to 6, and heating to a temperature sufiicient to evaporatethe water of reaction and said volatile hydrocarbon solvent, Wherein theamount of resulting metal salt comprises about 5 to 40 wt. percent ofthe final lubrieating composition.

2. A method according to claim 1, wherein said alkaline earth metal baseis lime, said C to C fatty acid is acetic acid, said C to C fatty acidis a mono-unsaturated C acid and n is about 3.

3. A method of preparing a lubricating grease which comprisesneutralizing 4 to 15 molar proportions of acetic acid and a molarproportion of C to C fatty acid with lime, in a volatile inerthydrocarbon solvent while maintaining the temperature below about 200F., homogenin ing the resultant mixture and filtering, then slowlymixing into said mixture polyphenyl ether lubricating oil of the generalformula:

Where n is 3 to 6 while stirring, heating the resulting mixture to atemperature within the range of about 250 to 450 F. in order todehydrate the mixture and evaporate the volatile solvent, and thencooling to thereby form said grease, wherein the amount of resultingmetal salt comprises about 10 to 30 wt. percent of said grease.

References Cited by the Examiner UNITED STATES PATENTS 2,844,534 7/58Cottle et al. 252-405 X 2,846,392 8/58 Morway et al 252-41 X 2,940,9296/60 Diamond 252- 35 X FOREIGN PATENTS 778,651 7/57 Great Britain.

DANIEL E. WYMAN, Primary Examiner.

JOSEPH R. LIBERMAN, Examiner.

1. A METHOD OF PREPARING A LUBRICATING COMPOSITION WHICH COMPRISESMIXING C2 TO C4 FATTY ACID AND C7 TO C30 FATTY ACID IN A RATIO OF ABOUT4 TO 30 MOLE EQUIVALENTS OF C2 TO C4 FATTY ACID PER MOLE EQUIVALENT OFC7 TO C30 FATTY ACID, WITH A NEUTRALIZING AMOUNT OF ALKALINE EARTH METALBASEM IN A VOLATILE INERT HYDROCARBON SOLVENT, ADDING POLYPHENYL ETHEROF THE GENERAL FORMULA: